minix/servers/rs/exec.c
Thomas Veerman 0bd011affd PM: extend srv_fork to set a specific UID
Currently, all servers and drivers run as root as they are forks of
RS. srv_fork now tells PM with which credentials to run the resulting
fork. Subsequently, PM lets VFS now as well.

This patch also fixes the following bugs:
 - RS doesn't initialize the setugid variable during exec, causing the
   servers and drivers to run setuid rendering the srv_fork extension
   useless.
 - PM erroneously tells VFS to run processes setuid. This doesn't
   actually lead to setuid processes as VFS sets {r,e}uid and {r,e}gid
   properly before checking PM's approval.
2012-01-30 15:16:19 +00:00

452 lines
12 KiB
C

#include "inc.h"
#include <a.out.h>
#include <assert.h>
#include <libexec.h>
#include "exec.h"
#define BLOCK_SIZE 1024
static int do_exec(int proc_e, char *exec, size_t exec_len, char *progname,
char *frame, int frame_len);
static int exec_newmem(int proc_e, vir_bytes text_addr,
vir_bytes text_bytes, vir_bytes data_addr,
vir_bytes data_bytes, vir_bytes tot_bytes,
vir_bytes frame_len, int sep_id, int is_elf,
dev_t st_dev, ino_t st_ino, time_t ctime, char *progname,
int new_uid, int new_gid, vir_bytes *stack_topp,
int *load_textp, int *allow_setuidp);
static void patch_ptr(char stack[ARG_MAX], vir_bytes base);
static int exec_restart(int proc_e, int result, vir_bytes pc);
static int read_seg(struct exec_info *execi, off_t off,
int proc_e, int seg, vir_bytes seg_addr, phys_bytes seg_bytes);
static int load_aout(struct exec_info *execi);
static int load_elf(struct exec_info *execi);
/* Array of loaders for different object formats */
static struct exec_loaders {
int (*load_object)(struct exec_info *);
} const exec_loaders[] = {
{ load_aout },
{ load_elf },
{ NULL }
};
int srv_execve(int proc_e, char *exec, size_t exec_len, char **argv,
char **UNUSED(Xenvp))
{
char * const *ap;
char * const *ep;
char *frame;
char **vp;
char *sp, *progname;
size_t argc;
size_t frame_size;
size_t string_off;
size_t n;
int ov;
int r;
/* Assumptions: size_t and char *, it's all the same thing. */
/* Create a stack image that only needs to be patched up slightly
* by the kernel to be used for the process to be executed.
*/
ov= 0; /* No overflow yet. */
frame_size= 0; /* Size of the new initial stack. */
string_off= 0; /* Offset to start of the strings. */
argc= 0; /* Argument count. */
for (ap= argv; *ap != NULL; ap++) {
n = sizeof(*ap) + strlen(*ap) + 1;
frame_size+= n;
if (frame_size < n) ov= 1;
string_off+= sizeof(*ap);
argc++;
}
/* Add an argument count and two terminating nulls. */
frame_size+= sizeof(argc) + sizeof(*ap) + sizeof(*ep);
string_off+= sizeof(argc) + sizeof(*ap) + sizeof(*ep);
/* Align. */
frame_size= (frame_size + sizeof(char *) - 1) & ~(sizeof(char *) - 1);
/* The party is off if there is an overflow. */
if (ov || frame_size < 3 * sizeof(char *)) {
errno= E2BIG;
return -1;
}
/* Allocate space for the stack frame. */
frame = (char *) malloc(frame_size);
if (!frame) {
errno = E2BIG;
return -1;
}
/* Set arg count, init pointers to vector and string tables. */
* (size_t *) frame = argc;
vp = (char **) (frame + sizeof(argc));
sp = frame + string_off;
/* Load the argument vector and strings. */
for (ap= argv; *ap != NULL; ap++) {
*vp++= (char *) (sp - frame);
n= strlen(*ap) + 1;
memcpy(sp, *ap, n);
sp+= n;
}
*vp++= NULL;
#if 0
/* Load the environment vector and strings. */
for (ep= envp; *ep != NULL; ep++) {
*vp++= (char *) (sp - frame);
n= strlen(*ep) + 1;
memcpy(sp, *ep, n);
sp+= n;
}
#endif
*vp++= NULL;
/* Padding. */
while (sp < frame + frame_size) *sp++= 0;
(progname=strrchr(argv[0], '/')) ? progname++ : (progname=argv[0]);
r = do_exec(proc_e, exec, exec_len, progname, frame, frame_size);
/* Return the memory used for the frame and exit. */
free(frame);
return r;
}
static int do_exec(int proc_e, char *exec, size_t exec_len, char *progname,
char *frame, int frame_len)
{
int r;
vir_bytes vsp;
struct exec_info execi;
int i;
execi.proc_e = proc_e;
execi.image = exec;
execi.image_len = exec_len;
strncpy(execi.progname, progname, PROC_NAME_LEN-1);
execi.progname[PROC_NAME_LEN-1] = '\0';
execi.frame_len = frame_len;
for(i = 0; exec_loaders[i].load_object != NULL; i++) {
r = (*exec_loaders[i].load_object)(&execi);
/* Loaded successfully, so no need to try other loaders */
if (r == OK) break;
}
/* No exec loader could load the object */
if (r != OK) {
printf("RS: do_exec: loading error %d\n", r);
return r;
}
/* Patch up stack and copy it from RS to new core image. */
vsp = execi.stack_top;
vsp -= frame_len;
patch_ptr(frame, vsp);
r = sys_datacopy(SELF, (vir_bytes) frame,
proc_e, (vir_bytes) vsp, (phys_bytes)frame_len);
if (r != OK) {
printf("RS: stack_top is 0x%lx; tried to copy to 0x%lx in %d\n",
execi.stack_top, vsp, proc_e);
printf("do_exec: copying out new stack failed: %d\n", r);
exec_restart(proc_e, r, execi.pc);
return r;
}
return exec_restart(proc_e, OK, execi.pc);
}
static int load_aout(struct exec_info *execi)
{
int r;
int hdrlen, sep_id, load_text, allow_setuid;
vir_bytes text_bytes, data_bytes, bss_bytes;
phys_bytes tot_bytes;
off_t off;
uid_t new_uid;
gid_t new_gid;
int proc_e;
assert(execi != NULL);
assert(execi->image != NULL);
proc_e = execi->proc_e;
/* Read the file header and extract the segment sizes. */
r = read_header_aout(execi->image, execi->image_len, &sep_id,
&text_bytes, &data_bytes, &bss_bytes,
&tot_bytes, &execi->pc, &hdrlen);
if (r != OK)
{
return r;
}
new_uid= getuid();
new_gid= getgid();
allow_setuid = 0;
/* XXX what should we use to identify the executable? */
r= exec_newmem(proc_e, 0 /*text_addr*/, text_bytes,
0 /*data_addr*/, data_bytes + bss_bytes, tot_bytes,
execi->frame_len, sep_id, 0 /*is_elf*/, 0 /*dev*/, proc_e /*inum*/, 0 /*ctime*/,
execi->progname, new_uid, new_gid, &execi->stack_top, &load_text,
&allow_setuid);
if (r != OK)
{
printf("RS: load_aout: exec_newmem failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
off = hdrlen;
/* Read in text and data segments. */
if (load_text) {
r= read_seg(execi, off, proc_e, T, 0, text_bytes);
if (r != OK)
{
printf("RS: load_aout: read_seg failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
}
else
printf("RS: load_aout: not loading text segment\n");
off += text_bytes;
r= read_seg(execi, off, proc_e, D, 0, data_bytes);
if (r != OK)
{
printf("RS: load_aout: read_seg failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
return OK;
}
static int load_elf(struct exec_info *execi)
{
int r;
int proc_e;
phys_bytes tot_bytes; /* total space for program, including gap */
vir_bytes text_vaddr, text_paddr, text_filebytes, text_membytes;
vir_bytes data_vaddr, data_paddr, data_filebytes, data_membytes;
off_t text_offset, data_offset;
int sep_id, is_elf, load_text, allow_setuid;
uid_t new_uid;
gid_t new_gid;
assert(execi != NULL);
assert(execi->image != NULL);
proc_e = execi->proc_e;
/* Read the file header and extract the segment sizes. */
r = read_header_elf(execi->image, &text_vaddr, &text_paddr,
&text_filebytes, &text_membytes,
&data_vaddr, &data_paddr,
&data_filebytes, &data_membytes,
&execi->pc, &text_offset, &data_offset);
if (r != OK) {
return(r);
}
new_uid= getuid();
new_gid= getgid();
allow_setuid = 0;
sep_id = 0;
is_elf = 1;
tot_bytes = 0; /* Use default stack size */
r = exec_newmem(proc_e,
trunc_page(text_vaddr), text_membytes,
trunc_page(data_vaddr), data_membytes,
tot_bytes, execi->frame_len, sep_id, is_elf,
0 /*dev*/, proc_e /*inum*/, 0 /*ctime*/,
execi->progname, new_uid, new_gid,
&execi->stack_top, &load_text, &allow_setuid);
if (r != OK)
{
printf("RS: load_elf: exec_newmem failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
/* Read in text and data segments. */
if (load_text) {
r = read_seg(execi, text_offset, proc_e, T, text_vaddr, text_filebytes);
if (r != OK)
{
printf("RS: load_elf: read_seg failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
}
else
printf("RS: load_elf: not loading text segment\n");
r = read_seg(execi, data_offset, proc_e, D, data_vaddr, data_filebytes);
if (r != OK)
{
printf("RS: load_elf: read_seg failed: %d\n", r);
exec_restart(proc_e, r, execi->pc);
return r;
}
return(OK);
}
/*===========================================================================*
* exec_newmem *
*===========================================================================*/
static int exec_newmem(
int proc_e,
vir_bytes text_addr,
vir_bytes text_bytes,
vir_bytes data_addr,
vir_bytes data_bytes,
vir_bytes tot_bytes,
vir_bytes frame_len,
int sep_id,
int is_elf,
dev_t st_dev,
ino_t st_ino,
time_t ctime,
char *progname,
int new_uid,
int new_gid,
vir_bytes *stack_topp,
int *load_textp,
int *allow_setuidp
)
{
int r;
struct exec_newmem e;
message m;
e.text_addr = text_addr;
e.text_bytes= text_bytes;
e.data_addr = data_addr;
e.data_bytes= data_bytes;
e.tot_bytes= tot_bytes;
e.args_bytes= frame_len;
e.sep_id= sep_id;
e.is_elf= is_elf;
e.st_dev= st_dev;
e.st_ino= st_ino;
e.enst_ctime= ctime;
e.new_uid= new_uid;
e.new_gid= new_gid;
e.setugid= *allow_setuidp;
strncpy(e.progname, progname, sizeof(e.progname)-1);
e.progname[sizeof(e.progname)-1]= '\0';
m.m_type= EXEC_NEWMEM;
m.EXC_NM_PROC= proc_e;
m.EXC_NM_PTR= (char *)&e;
r= sendrec(PM_PROC_NR, &m);
if (r != OK)
return r;
#if 0
printf("exec_newmem: r = %d, m_type = %d\n", r, m.m_type);
#endif
*stack_topp= m.m1_i1;
*load_textp= !!(m.m1_i2 & EXC_NM_RF_LOAD_TEXT);
*allow_setuidp= !!(m.m1_i2 & EXC_NM_RF_ALLOW_SETUID);
#if 0
printf("RS: exec_newmem: stack_top = 0x%x\n", *stack_topp);
printf("RS: exec_newmem: load_text = %d\n", *load_textp);
#endif
return m.m_type;
}
/*===========================================================================*
* exec_restart *
*===========================================================================*/
static int exec_restart(int proc_e, int result, vir_bytes pc)
{
int r;
message m;
m.m_type= EXEC_RESTART;
m.EXC_RS_PROC= proc_e;
m.EXC_RS_RESULT= result;
m.EXC_RS_PC= (void*)pc;
r= sendrec(PM_PROC_NR, &m);
if (r != OK)
return r;
return m.m_type;
}
/*===========================================================================*
* patch_ptr *
*===========================================================================*/
static void patch_ptr(
char stack[ARG_MAX], /* pointer to stack image within PM */
vir_bytes base /* virtual address of stack base inside user */
)
{
/* When doing an exec(name, argv, envp) call, the user builds up a stack
* image with arg and env pointers relative to the start of the stack. Now
* these pointers must be relocated, since the stack is not positioned at
* address 0 in the user's address space.
*/
char **ap, flag;
vir_bytes v;
flag = 0; /* counts number of 0-pointers seen */
ap = (char **) stack; /* points initially to 'nargs' */
ap++; /* now points to argv[0] */
while (flag < 2) {
if (ap >= (char **) &stack[ARG_MAX]) return; /* too bad */
if (*ap != NULL) {
v = (vir_bytes) *ap; /* v is relative pointer */
v += base; /* relocate it */
*ap = (char *) v; /* put it back */
} else {
flag++;
}
ap++;
}
}
/*===========================================================================*
* read_seg *
*===========================================================================*/
static int read_seg(
struct exec_info *execi, /* various data needed for exec */
off_t off, /* offset in file */
int proc_e, /* process number (endpoint) */
int seg, /* T, D, or S */
vir_bytes seg_addr, /* address to load segment */
phys_bytes seg_bytes /* how much is to be transferred? */
)
{
/*
* The byte count on read is usually smaller than the segment count, because
* a segment is padded out to a click multiple, and the data segment is only
* partially initialized.
*/
int r;
assert((seg == T)||(seg == D));
if (off+seg_bytes > execi->image_len) return ENOEXEC;
r= sys_vircopy(SELF, D, ((vir_bytes)execi->image)+off, proc_e, seg, seg_addr, seg_bytes);
return r;
}